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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 6 · 40 sums
TalentJR

The method (Inside 180, outside the sum): Angle sum: ∠A + ∠B + ∠C = 180°. Exterior angle = sum of the two interior opposite angles. Right-angled triangle: longest side² = side² + side² (3, 4, 5 and 5, 12, 13 are famous sets). Sides can make a triangle only if the two shorter sides add up to more than the longest side.

NameDateTime takenScore ___ / 40
  1. 1.Can a triangle have sides of 9 cm, 20 cm and 6 cm? (a) No (b) Yes
  2. 2.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  3. 3.In triangle ABC, angle A = 57° and angle B = 65°. What is angle C (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  5. 5.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  6. 6.Can a triangle have sides of 7 cm, 22 cm and 12 cm? (a) Yes (b) No
  7. 7.In triangle ABC, angle A = 73° and angle B = 26°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 59° and angle B = 49°. What is angle C (in degrees)?
  9. 9.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  10. 10.In triangle ABC, angle A = 26° and angle B = 85°. What is angle C (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 29° and 63°. What is the exterior angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  13. 13.In triangle ABC, angle A = 78° and angle B = 45°. What is angle C (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  16. 16.In triangle ABC, angle A = 64° and angle B = 23°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  19. 19.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  20. 20.An exterior angle of a triangle is 121°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  21. 21.In triangle ABC, angle A = 25° and angle B = 70°. What is angle C (in degrees)?
  22. 22.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 77° and 47°. What is the exterior angle (in degrees)?
  25. 25.Can a triangle have sides of 9 cm, 19 cm and 6 cm? (a) Yes (b) No
  26. 26.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  27. 27.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 99° and angle B = 27°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 84° and angle B = 33°. What is angle C (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 62° and angle B = 45°. What is angle C (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 31° and angle B = 23°. What is angle C (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 60° and angle B = 63°. What is angle C (in degrees)?
  37. 37.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 25° and 22°. What is the exterior angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?

Answer key

  1. No
  2. 67
  3. 58
  4. 17
  5. 54
  6. No
  7. 81
  8. 72
  9. 9
  10. 69
  11. 92
  12. 90
  13. 57
  14. 45
  15. 44
  16. 93
  17. 14
  18. 36
  19. 36
  20. 44
  21. 85
  22. 50
  23. 80
  24. 124
  25. No
  26. 65
  27. 68
  28. 32
  29. 54
  30. 63
  31. 22
  32. 73
  33. 32
  34. 126
  35. 62
  36. 57
  37. 34
  38. 90
  39. 47
  40. 63

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